1. Field of the Invention
The present invention generally relates to an arrangement for, and a method of, reducing image distortion due to electrical interference, especially for use in a color image projection system operative for projecting a two-dimensional image in color while maintaining low power consumption, high resolution, miniature compact size, quiet operation and minimal vibration.
2. Description of the Related Art
It is generally known to project a two-dimensional image on a screen based on a pair of scan mirrors which oscillate by respective drives in mutually orthogonal directions to scan a laser beam over a raster pattern. However, the known image projection arrangements project the image with limited resolution, typically less than a fourth of video-graphics-array (VGA) quality of 640×480 pixels, consume a relatively large amount of electrical power, and are relatively heavy in weight and occupy a relatively large volume, thereby rendering them impractical for use in miniature, hand-held, battery-operated applications. The image also suffers from electrical interference.
For example, the drive for one of the scan mirrors includes a permanent magnet jointly movable with the mirror. The magnet and the mirror are mounted on a flexure that permits oscillation about an axis. An electromagnetic coil is energized by a periodic drive signal having a drive frequency and generates an electromagnetic field which interacts with the permanent field of the magnet to flex the flexure and cause the magnet and, in turn, the scan mirror to move in one direction about the axis at a constant drive speed. The scan mirror is self-returnable at a resonant frequency in an opposite direction about the axis at a return speed greater than the drive speed.
Although generally satisfactory for its intended purpose, the above-described electromagnetic drive is not ideal for projecting a non-distorted image. For example, the drive frequency of the drive signal and/or an AC supply line frequency for energizing the drive and/or harmonics of the drive frequency and the line frequency may electrically interfere with the resonant frequency and with one another, thereby corrupting the constant drive speed and leading to image distortion.